Question

Velocities of four gas molecules are $2,3,-4,-1m/sec$ respectively.
Then choose the correct statements
I. the mean velocity of molecules is zero
II. the mean speed of molecules is $2.5m/s$
III. the mean square velocity of molecules is $7.5m^2/s^2$
IV. the root mean square velocity of molecules is $2.74m/s$

• A. I and II
• B. II and IV
• C. I and III
• D. I, II, III and IV

Answer 1

Answer: (D)

Mean velocity $=\frac{2+3-4-1}{4}=0$,
Mean speed $=\frac{2+3+4+1}{4}=2.5$,
Mean square speed $=\frac{2^2+3^2+4^2+1^2}{4}=7.5m^2/s^2$,
$V_{rms}=\sqrt{7.5}=2.74m/s$